Last year I purchased the Canon Xs rebel with the EFS 3.5 18-55mm lens (came with the kit). If I had waited I could have purchased the T2i...who would have known? For this camera, I also have a Canon EF 50mm 1.8 lens as well.
Both lenses I really need room to shoot photography (have to stand back far) and can't get too close either since they are not macro lenses
So what kind of lens would be a nice addition for videography?
I have seen the Canon EF 70-300mm quite cheap, but I am assuming there is a reason for it inexpensive nature.

This blog had a nice article describing some inexpensive starting lenses for the t2i:

On a budget? Pimp your new Canon EOS Rebel T2i / 550D with essential accessories! Part 1: BASIC LENSES | Nino Film - Blog - Nino Leitner (http://ninofilm.net/blog/2010/03/01/pimp-t2i-550d-part1/)

If you have very little money, buy the Canon EF 50mm f/1.8 II. If you have a bit more, get the Sigma 30mm f/1.4 EX DC HSM and/or Canon EF 50mm f1.4 USM. And if you can afford it, definitely get the Canon EF 24-70mm f/2.8L USM standard zoom.

You already have the 50? so maybe look at that fast wide angle, or a nicer zoom.

Here is a good discussion of lens options for the T2i/ 550D or 7D.

http://www.dvinfo.net/forum/canon-eos-rebel-t2i-eos-550d-hd/473955-if-you-could-only-use-3-lenses.html